Islamic State official spokesman al-Adnani announced dead in Syria's Aleppo

Quoting a "military source", the Islamist group's Amaq News Agency reported the jihadi was killed "while surveying the operations to repel the military campaigns against Aleppo".

A USA counter-terrorism official who monitors Islamic State said Adnani's death will hurt the militants "in the area that increasingly concerns us as the group loses more and more of its caliphate and its financial base. and turns to mounting and inspiring more attacks in Europe, Southeast Asia and elsewhere".

Adnani was originally from the western Syrian province of Idlib and joined the jihadist movement in Iraq, where he served now slain Al-Qaeda leader Abu Musab al-Zarqawi and held several positions.

It said he died after a "long voyage crowned by sacrifice" and vowed "revenge" at the hands of a "new generation born unto the Islamic State".

Aymenn Jawad Tamimi, an expert on jihadist groups, said Adnani's death was "significant symbolically and in pointing to the wider decline of the Islamic State". "The U.S. military will continue to prioritize and relentlessly target ISIS leaders and external plotters in order to defend our homeland, our allies and our partners, while we continue to gather momentum in destroying ISIL's parent tumor in Iraq and Syria and combat its metastases around the world".

Analysts have described Adnani as a key figure in the jihadist group.

Adnani was believed to be one of the first foreign fighters against U.S. troops in Afghanistan before joining ISIS

Adnani was reported to have been seriously injured eight months ago in Iraq, during fighting near the city of Haditha. He was the first ISIS official to announce the group's self-declared Caliphate in Syria and Iraq in June 2014.

US officials did not immediately comment on the reported death of al-Adnani because it had yet to be independently verified.

Amaq did not say how Adnani was "martyred".

A senior Islamic State leader who had a $5 million US bounty on his head has been killed in fighting in Syria, the Amaq News Agency reported Tuesday. They described him as "the official spokesman for and a senior leader" of ISIS, a position he obtained after becoming one of the first foreign fighters to oppose US -led coalition forces in Iraq. "If you can't do that then drive your cars, your vehicles, to kill them", Robertson said.

The U.S. State Department offered a $5 million reward past year for information leading to Adnani's capture.

In May 2016 he issued a statement calling for the execution of so-called lone-wolf attacks in countries preventing jihadis from travelling to Iraq and Syria to fight alongside the Islamic State.